This invention relates to a distance information obtaining device for use in obtaining distance information for a robot arm or a magic hand.
A distance information obtaining device is disclosed in an article which is published by Johji Tajima, the instant applicant, under the title of "Rainbow Range Finder Principle for Range Data Acquisition" in "International Workshop on Industrial Application of Machine Vision and Machine Intelligence", pages 381 to 386, and which was held by IEEE on 1987. A range finder is used as the distance information device.
In order to deal with an object by using a robot arm, it is necessary to sense distance information from an observation position to each point on the object. The range finder is for obtaining the distance information by using a picture signal of the object. The range finder therefore comprises an image pickup device, such as a color television camera, which is located at the observation position. The image pickup device has a pickup axis directed towards the object. The image pickup device comprises first and second photoelectric transducers having first and second spectral sensitivities which are different from each other.
A diffraction grating is used in illuminating the object by a monochromatic beam of a wavelength .lambda.. The diffraction grating is located at a grating position spaced apart from the observation position and has a normal directed towards the object. The monochromatic beam is projected onto a specific point of the object with a beam angle .theta. formed between the normal of the diffraction grating and the monochromatic beam. In other words, the monochromatic beam is projected onto the specific point at a first angle .alpha. with the pickup axis.
Towards the image pickup device, the specific point reflects the monochromatic beam as a reflected beam which forms a second angle .beta. with the pickup axis. The first and the second photoelectric transducers produce first and second picture signals in response to the reflected beam.
The range finder further comprises a processing unit for processing the first and the second picture signals. As will later be described more in detail, the first and the second picture signals are processed for searching the wavelength .lambda.. The beam angle .theta. is decided in accordance with the wavelength .lambda. and is used for determining the first angle .alpha.. A predetermined calculation is carried out by using information of the diffraction position and the first and the second angles .alpha. and .beta.. The predetermined calculation is successively carried out as regards each picture element of the first and the second picture signals. In other words, the predetermined calculation is carried out for each point of the object. For this purpose, beams reflected at the respective points are picked up by the image pickup device.
The conventional range finder requires the information of the grating position and the first and the second angles as initial values. Furthermore, the initial values must be measured each time when the grating or the pickup device is subjected to failure and is changed to a new grating or pickup device.